Biological membranes - Temperature and Solvents

Question 1

what is the effect of an increase in temperature on membranes

Answer 1

increase in kinetic energy, increase in movement, more fluid, permeable membranes

Question 2

why do high temperatures cause the membrane to become more permeable

Answer 2

phospholipids vibrate, causing them to be further apart. the bigger gaps allow larger molecules to pass through, the phospholipid bilayer is therefore more permeable

Question 3

what is the impact of very high temperatures on membranes

Answer 3

cause the phospholipids to move completely apart, causing the membrane to break down

Question 4

what will happen to protein structure in the membrane as temperature is increased

Answer 4

bonds broken, secondary and tertiary structure changed, protein denatured

Question 5

how does the structure of membranes vary in organisms at high and low temperatures

Answer 5

high temp - increased cholesterol, less unsaturated fatty acids in phospholipids
low temp - decreased cholesterol, more unsaturated fatty acids in phospholipids (more kinks)

Question 6

describe and explain the effect of organic solvents on membrane permeability

Answer 6

• organic solvents are less polar than water and can dissolve lipids.
• ethanol dissolves the lipids in the cell membrane, which means the membrane loses its structure.
• increasing the concentration of the solvent will increase permeability of membranes

Question 7

what is the effect of very strong alcohol solutions

Answer 7

destroy cells

Question 8

why is alcohol found in antiseptic wipes

Answer 8

will dissolve membranes of bacteria, killing them and reducing infection

Question 9

why does water not disrupt cell membranes

Answer 9

it is polar and cannot dissolve phospholipids